1. Field of the Invention
The present invention relates to a paper cassette. More particularly, the present invention relates to a paper cassette that is detachably coupled to an image forming apparatus and is adapted to receive a large number of paper sheets.
2. Description of the Related Art
Examples of image forming apparatuses include a printer, a copying machine, a facsimile, and a multi-function device. An image forming apparatus includes a main body for printing an image and a paper feeder for supplying paper to the main body. Herein, the term “paper” is used to denote all kinds of printing media, such as paper, photographic paper, OHP film, and so forth.
The paper feeder may include a paper cassette detachably coupled to the image forming apparatus in the form of a drawer, a knock-up plate formed in the paper cassette for receiving paper, a knock-up spring urging the knock-up plate toward a pick-up roller for elastically pressing a leading end of the paper against an outer surface of the pick-up roller, a hinge allowing the rotation of the knock-up plate, and a hinge hole receiving the hinge. One end of the knock-up plate is rotatably fixed by the hinge and the hinge hole, and the other end is elastically biased by the knock-up spring. The slope of the knock-up plate is changed by the hinge inserted into the hinge hole according to the number of paper sheets loaded on the knock-up plate. In the image forming apparatus, the pick-up roller is located above the knock-up plate. The pick-up roller makes contact with a leading end of paper loaded on the knock-up plate to supply the paper to the main body of the image forming apparatus one sheet by one sheet. The pick-up roller is coupled to a pick-up roller shaft and is rotated by a pick-up roller driving unit.
The paper feeder can receive sheets of paper having various sizes, such as A6 (105×148 mm), A5 (148×210 mm), B5 (182×257 mm), A4 (210×297 mm), letter (216×297 mm), and legal (216×356 mm). To receive paper of various sizes, the paper cassette of the paper feeder must be larger than the largest paper sheet to be loaded in the paper cassette.
However, the size of the paper cassette should be reduced to provide a smaller image forming apparatus. For example, although the width of an image forming apparatus should be larger than that of A4 paper to print an image on the A4 paper, the length of the image forming apparatus can be smaller than that of the A4 paper. In this case, a paper cassette may protrude from the image forming apparatus when the paper cassette is installed since the paper cassette should be wider and longer than the A4 paper to store the A4 paper. This decreases the cosmetic appearance of the image forming apparatus and increases the package size and installation space of the image forming apparatus.
Accordingly, a need exists for an image forming apparatus having an improved paper cassette.